1. Field of the Invention
The present invention relates to a noise prevention high voltage resistive wire used as ignition cords for automotive vehicles, and more specifically to an improvement of the resistive wire including terminals attached thereto.
2. Description of the Prior Art
In ignition cords used for an automotive vheicle, conventionally, the cord wire is a conductor made of a material having a high resistance such as nonmetal; the core wire is covered by an insulating material; and two metallic terminals are fixed to both free ends of the resistive wire.
The ignition cord is usually used for conducting high voltage large pulse current from a distributer to ignition plugs, and therefore, the metallic terminals are formed into a cylindrical shape so as to be appropriately connectable to ignition plugs.
FIG. 1 shows an example of prior art noise prevention high voltage resistive wires in which the reference numeral 1 denotes a high voltage resistive wire; and 2 denotes a metallic terminal 2, and 3 denotes a conductive bonding agent 3. The resistive wire 1 includes an insulating material 1a and a core wire 1b; the terminal 2 includes two caulking tabs 2a and a radial plate 2b. The terminal 2 is connected to the resistive wire 1 by caulking the two caulking tabs 2a onto the outer surface of the resistive wire 1 in such a way that the core wire 1b is in contact with the radial plate 2b of the terminal 2. This radial plate 2b is effective to secure the contact between the terminal 2 and the core wire 1b while increasing the contact area between the two, when the terminal 2 is fixed to the resistive wire 1. Further, in FIG. 1, an exposed end of the core wire 1b is bent into a hook shape so as to be sandwiched between the outer surface of the insulating material 1a and the inner surface of the terminal 2.
In the resistive wire as described above, however, corona discharge will readily be generated at the metallic terminals due to unstable contact between the terminal and the core wire, when a high voltage large current flows therethrough, thus often resulting in a burning trouble due to corona discharge. To overcome this problem, a method has been proposed by which a conductive bonding agent is first applied to an end of the core wire 1b and then the terminal 2 is fitted to the resistive wire 1 to bond the core wire end to the radial plate 2b.
Recently, however, there exists a tendency toward a higher ignition voltage in proportion to higher engine compression ratio with increasing engine performance in automotive vehicles. Therefore, there still exists a problem in that corona discharge is often generated at the terminals of the resistive wire. In addition, where heat-cool cycle is repeated and further vibration is applied to the resistive wire, small gaps inevitably remaining at the bonding area will inevitably produce cracks thereat, thus resulting in partial peeling-off of the bonding agent and further resistive wire burning trouble.